Filament connection for electric lamps



June 13, "1944.

R. E. SMITH 2,351,299

FILAMENT CONNECTION FOR ELECTRIC LAMPS Filed Oct. 11, 1943 I Fig 3 2 'lnvewtor:

Richard E. Smiirh,

. His A=ttorne3 Patented June 13, 1944. a

2,351,299 I FILAMEN T CONN EOTION FOR ELECTRIC .LAMPS Richard E. Smith, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application October 11, 1943, Serial No. 505,734 6 Claims. (01. 176-38) My invention relates in general to electric 1ncandescent lamps and similar devices, and more particularly to high wattage lamps and devices. Still more particularly, my invention relates to an improved joint or connection between the filament and lead-in wires of such devices.

In certain types of electric incandescent lamps, particularly lamps of the high wattage type, it has been found advantageous to increase the current-carrying capacity of the filament wire at and near the welded connections thereof to the lead-in wires. This is usually accomplished either by providing a slipover coil on each of the end legs of the filament, or by coiling the end legs of the filament and inserting a spud wire therein. Both of these methods, however, have the disadvantage that a more or less heavy weld resulting in excessive movement or embedding of the filament end legs into the lead-in wires is necessary if a good, strong welded-joint is to be obtained therebetween. Where the filament is held in a jig during its attachment to the lead-in wires, such excessive movement of the filament end legs is then apt to set up stresses in the fllament which tend to pull the segments thereof out of correct position upon removal of the filament-holding jig after the completion of the joint welding operation.

One object of my invention is to provide an improved jointbr connection between the fllament and lead-in wires of an electric incandescent lamp or similar device.

Another object of my invention is to provide, in an electric incandescent lamp of the type having a filament provided with a composite end conductor consisting of a coil with a core extending therethrough, a strong welded joint between the filament end conductor and a lead-in wire which can be produced with a minimum amount of movement of the composite conductor relative to the lead-in wire during the welding operation.

Still another object of my invention is to provide a strong welded filament joint between a jig-held filament of the above type and an elec tric lamp lead-in wire which joint can be produced without setting up excessive stresses in the jig-held filament such as might result in displacement of the filament from its jig-held position upon completion of the joint and removal of the portion which is welded to the lamp lead-in wire alongside the conducting core member that passes through the slipover coil.

Further objects and advantages of my invention will appear from the following description of species thereof and from the accompanying drawing in which:

Fig. 1 is an elevation, in section, of an electric incandescent lamp having a filament joint comprising my invention; Fig. 2 is a perspective view on an enlarged scale of the mount structure of the lamp shown in Fig. 1; Fig. 3 is an elevation, partly in section and On an enlarged scale, of the filament joint comprising my invention; and Fig. 4 is a perspective view of a modified form of filament joint according to the invention.

Referring to the drawing, the lamp there shown is of the self-contained reflector type described and claimed in U. S. Patents Nos. 2,148,314 and 2,148,315-D. K. Wright, issued February 21, 1939,

and assigned to the assignee of the present invention; The lamp comprises a bulb or envelope Ill consisting of a preformed pressed glass reflector section II fused around its periphery to a preformed pressed glass cover section i2. The interior surface of the reflector section II is of a light-concentrating shape, preferably paraboloidal, and is covered with a reflecting coating I3, preferably of aluminum, constituting a refleeting surface. Mounted on the reflector section ll, exteriorly thereof and at the apex of said section, is a base structure it. The said, base structure M is suitably secured, as by soldering,

to metallic cups or thimbles i5 having their edges sunk and embedded in the glass of the reflector section II around openings l8 therein, the cups or thimbles l5 thus hermetically closing the openings It. The envelope ii! is exhausted and filled with a suitable gas through an exhaust tube ll attached to the reflector section it at its apex. After the gas filling is introduced into the lamp envelope, the exhaust tube I1 is tipped 0fl,'as indicated at I8, to hermetically seal the envelope.

Mounted within the envelope Ill and supported therein from the metal thimbles I5 is a mount structure l9 comprising an electric energy translation element or filament 20 disposed between and connected to a pair of rigid lead-in wires or conductors 2|, 2|. The lead-in wires 2i are rigidly secured at their outer ends to the metal thimbles l5, as by soldering, and extend through the openings IS in the reflector section into the interior of said envelope in parallel relation to one another. The lead-in wires 2| are held in rigid spaced relation by an insulating bridge or cross bar comprising a glass-rod 22 extending bctweenand secured to the lead-in wires 2| by short fastening wires 23 which may be spotwelded to the lead-in wires.

The filament is of the high wattage type comprising a plurality of coiled wire segments 24 of tungsten which extend in' the general direction of the reflector axis and are joined by a bight portion 25. The filament segments 24 are preferably disposed in the plane of the lead-in wires 2| and in a position in definite optical relation to the focus of the reflecting surface l3, preferably symmetrically about the refiector focus. The filament is supported in place at the bight portion 25 thereof by means of a support or anchor wire 26 having a hooked end 21 engaging the bight 25 and its other end rigidly secured to the glass rod 22 of the insulating bridge; as by embedding therein.

Each end of the filament 20 is provided with a straight uncoiled end section or leg portion 28 extending laterally of the adjacent lead-in wire 2| and welded thereto, as indicated at 29 in Fig. 3. A slipover coil 30, of b. suitable heat-resisting metal such as tungsten, tmolybdenum or an alloy thereof, is mounted on each filament end leg 28. The said slipover coil 30 is preferably made just large enough in diameter to fit more or less snugly around the filament end leg 28. The filament end legs 28, together with the associated slipover coils 30, thus form composite end conductor portions for the filament, the filament end legs 28 serving as core members for such composite conductors.

In accordance with the invention, each slipover coil 30 is wound with a closely-coiled inner end section 3| and a widely open-coiled outer end section 32. The open-coiled outer portion 32 of each slipover coil extends adjacent the lead-in wire 2| and is welded thereto alongside the filament end leg 28, as indicated at 33 in Fig. 3. This opencoiling of the outer end portion of the slipover coil, in addition to providing a more economical construction, also enables the welding of the filament legs 28 to the lead-in wires 2| with a minimum amount of movement of the filament legs relative to the lead-in wires. This is of considerable importance where the filament is to be attached to the lead-in wires in a predetermined position (such as at th focus of the reflector section II) and for that reason is held in a jig during the attachment of the filament to the lead-in wires, for in such case the small or negligible movement of the filament legs 28 relative to the jig-held segments 24 of th filament during the joint welding operation sets up little, if any, stress in the filament tending to pull the segments 24 thereof out of their original jig-held position upon removal of the jig following completion of the filament joint.

In the modified form of filament joint shown in Fig. 4, each end of the filament 20 is formed with an end coil 34 conforming in construction to the slipover coil 30 of Figs. 1-3. A straight spud wire 35 of a suitabl metal such as tungsten or molybdenum is inserted within the said end coil 34 to form, together with the filament end coil 34, a composite end conductor portion for the filament. The spud wire 35 and the opencoiled outer end section 32 of the filament end coil 34, are welded to the adjacent lead-in wire 2| in the same manner as the slip-over coil 30 and filament end leg 28 in Figs. 1-3 to thereby form the connection between the lead-in wire and the v filament.

What I claim as new and desire to secure by Letters Patent of the United States'is:

1. In an electric lamp, the combination of a lead-in wire, and a filament having a composite end portion comprising a coil with a core member extending therethrough, said core member and coil having portions thereof extending transversely across said lead-in wire in side-by-side relation and'being individually welded thereto at different points along the length of said lead-in wire.

2. In an electric lamp, the combination of a lead-in wire, and a filament having a composite end portion comprising a core member and a coil snugly fitted on said core member and having an open-coiled section, the core member and open coil section having portions thereof extending transversely across said lead-in wire in side-byside relation and being individually welded thereto at different points along the length of said lead-in wire.

3. In an electric lamp, the combination of a lead-in wire, a filament having an end section, and a slipover coil snugly fitted on said end section, said coil and filament end section having portions thereof extending transversely across said lead-in wire in side-by-side relation and being individually Welded thereto at different points along'the length of said lead-in wire.

4. In an electric lamp, the combination of a lead-in wire, a filament having an uncoiled end leg, and a wire slip-over coil snugly fitted on the said'filament end leg and having a widely opencoiled section, the filament and leg and open coil section having portions thereof extending transversely across said lead-in wire in side-by-side relation and being individually welded thereto at different points along the length of said lead-in wire.

5. In an electric lamp, the combination of a lead-in wire, a filament having an end coil, and a conductor extending through the said end coil, said conductor and filament end coil having portions thereof extending transversely across said lead-in wire in side-by-side relation and being individually welded thereto at different points along the length of said lead-in wire.

6. In an electric lamp, the combination of a lead-in wire, a filament having an end coil provided with a widely open-coiled section, and a spud wire extending through the said end coil,

the spud wire and open coil section having portions thereof extending transversely across said lead-in wire in side-by-sicle relation and being individually welded thereto at different points along the length of said lead-in wire.

RICHARD E. SMITH. 

